Update RELEASE_NOTES.md for 1.5.42 release

[Arkatufus]

1.5.42 May 21st, 2025

Akka.NET v1.5.42 contains several bug fixes and also adds new quality of life features to Akka.IO.Tcp, Akka.Persistence, Akka.Pattern, and Akka.Cluster.Tools.DistributedPubSub.

• IO.Tcp: Cleanup API
• IO.Tcp: Fix TcpListener connection queue problem
• Persistence: Allow user to use supervision strategy on journal and snapshot store
• Core: Add cancellation token to CircuitBreaker API to signal timed out operations
• Persistence: Change all CircuitBreaker protected method API to use cancellation token
• Core: Leverage Exception...when pattern
• IO.Tcp: Add TcpListenerStatistics and subscription methods
• Cluster.Tools: Modernize DistributedPubSub code
• Cluster.Tools: Optimize DistributedPubSub memory allocation
• Cluster.Tools: Improve DistributedPubSub DeadLetter log message
• Core: Refactor immutable collection builders to use simpler CreateBuilder pattern
• IO.Tcp: Redesign TcpConnection
• Cluster.Tools: Add PublishWithAck feature to DistributedPubSub

Warning

This release contains several public API breaking changes to Akka.IO.Tcp and Akka.Persistence

Akka.Pattern.CircuitBreaker

Backward compatible API changes:

• New .WithCircuitBreaker() APIs were added that changes the protected function delegate to accept a new CancellationToken argument.
• Old .WithCircuitBreaker() APIs were marked as obsolete.

Akka.Cluster.Tools.DistributedPubSub

The documentation for the new PublishWithAck feature can be read here

Backward compatible API changes:

• There is a new DistributedPubSubSettings constructor that leverages the new PublishWithAck feature. The old constructor is marked as obsolete.

Akka.Persistence

The documentation for the new supervision strategy for journal and snapshot-store feature can be read here

Breaking API changes:

Due to changes in CircuitBreaker.WithCircuitBreaker() APIs, several Akka.Persistence journal and snapshot-store were changed in a breaking manner. You will need to consider these changes if you have your own specific Akka.Persistence plugin implementation and needed to upgrade to this version of Akka.

• AsyncWriteJournal
  • DeleteMessagesToAsync()
  • ReadHighestSequenceNrAsync()
  • WriteMessagesAsync
• SnapshotStore
  • Both DeleteAsync() methods
  • LoadAsync()
  • SaveAsync()

Akka.IO.Tcp

The Akka.IO.Tcp has been redesigned to improve its reliability, visibility, and performance. This, unfortunately, requires some breaking changes to be introduced into the code base.

New features:

• The TcpListener actor now accepts a new SubscribeToTcpListenerStats message. Subscribers will receive regular TcpListenerStatistics metrics report from the TcpListener.
• The new UnsubscribeFromTcpListenerStats message can be used to unsubscribe from the TcpListener

Backward compatible changes:

• The Akka.IO.Tcp.Bind command now contain a new settable TcpSettings property.
• The Akka.IO.Tcp.Connect command now contain a new settable TcpSettings property.
• The Akka.IO.TcpSettings class have several of its unused properties deprecated and/or changed:
  • The ReceivedMessageSizeLimit property has been deprecated, replaced with the new MaxFrameSizeBytes property.
  • New ReceiveBufferSize property added.
  • New SendBufferSize property added.

Breaking API changes:

• Akka.IO.Tcp.Instance static field has been removed.
• Akka.IO.TcpExt.BufferPool static property has been removed.

To see the full set of changes in Akka.NET v1.5.42, click here.

5 contributors since release 1.5.41

COMMITS	LOC+	LOC-	AUTHOR
15	3480	2864	Aaron Stannard
5	1711	713	Gregorius Soedharmo
4	72	100	Simon Cropp
1	172	51	Arjen Smits
1	16	60	JuYoung Kim

[Arkatufus]

Still need to complete the breaking change notes